Earth bolt containing surface treatment layer and method of surface treatment of earth bolt

Abstract

An earth bolt with a surface treatment layer are a method of surface treatment of the earth bolt are provided. The surface treatment includes a tin-zinc plated layer, a colored chromate film layer and a silicate coating layer. Since the earth bolt with the surface treatment layer has improved electro-conductivity and anti-rusting property, it may protect electrical/electronic components fitted to a vehicle from electromagnetic shock and remove noise therefrom, thereby improving reliability of a vehicle body.

What is claimed is: 
     
       1. An earth bolt with a surface treatment layer including a plated layer, comprising:
 a tin-zinc plated layer; 
 a colored chromate film layer; and 
 a silicate coating layer, 
 wherein the tin-zinc plated layer is formed by plating with a plating solution containing tin of about 70 wt % or greater based on the total weight of the tin-zinc plating solution. 
 
     
     
       2. The earth bolt with the surface treatment layer according to  claim 1 , wherein the surface treatment layer has a sequentially laminated structure of a tin-zinc plated layer, a colored chromate film layer and a silicate coating layer from the surface of the earth bolt. 
     
     
       3. The earth bolt with the surface treatment layer according to  claim 1 , wherein the tin-zinc plated layer has a thickness of about 8 to 12 μm. 
     
     
       4. The earth bolt with the surface treatment layer according to  claim 1 , wherein the colored chromate film layer has a thickness of about 1 μm or less. 
     
     
       5. The earth bolt with the surface treatment layer according to  claim 1 , wherein the silicate coating layer has a thickness of about 1 μm or less. 
     
     
       6. A method for the surface treatment of an earth bolt, comprising:
 plating an earth bolt with a plating solution containing tin of about 70 wt % or greater based on the total weight of the tin-zinc plating solution, to form a tin-zinc plated layer; 
 forming a film on the tin-zinc plated layer using a solution including chromic acid or dichromate, to form a colored chromate film layer; and 
 applying a silicate solution on the colored chromate film layer, to form a silicate coating layer. 
 
     
     
       7. The method for the surface treatment according to  claim 6 , wherein the tin-zinc plated layer has a thickness of about 8 to 12 μm. 
     
     
       8. The method for the surface treatment according to  claim 6 , wherein the colored chromate film layer has a thickness of about 1 μm or less. 
     
     
       9. The method for the surface treatment according to  claim 6 , wherein the silicate coating layer has a thickness of about 1 μm or less.